Manufacture of cement.



I No. 738,388.

UNITED STATES Patented September 8, 1903.

PATENT- OFFICE.

WVILLIAM A. OTTO WUTI'I, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TOINTERNATIONAL CEMENT COMPANY, A CORPORATION OF NEIV JERSEY.

MANUFACTURE OF CEMENT.

SPECIFICATION forming; part of Letters Patent No. 738,388, datedSeptember s, 1903,

Application filed June 24,1902. Serial No. 1l3,021. (No specimens.)

To all whom it may concern.-

Be it known that I, WILLIAM A. Orro WUTH, a resident of Pittsburg, inthe coupty of Allegheny and State of Pennsylvania, have invented anewand usefulImprovementin the Manufacture of Cement, (Case No. 1;) andI do hereby declare the following to be a full, clear, and exactdescription thereof.

My invention relates to the manufacture of a cement similar to thatknown as Portland cement. I

In my Patent No. 643,856, granted February 20, 1900, I have describedand claimed a process of forming cement from blast-furnace slag, theprocess consisting, essentially, in hydrating burned lime with watercontaining a soluble salt which will evolve oxygen at a hightemperature, then mixing the hydrated lime with powdered blast-furnaceslag, and thereafter burning the mixture. In that patent it was pointedout that the usual ingredients of Portland cement are found in a properadmixture of lime and blast-furnace slag. The object of the processclaimed in the patent was to eliminate the sulfur from the blast-furnaceslag or, in other words, to reduce it from a sulfid to a harmlesssulfate.

The object of the present application is to claim a modification of theprocess described in the patent aforesaid, and the essential feature ofthe modification consists in using limestone in place of lime, therebyobviating the necessity of burning the lime and the frequent handlingsincident thereto. The final burning of the mixture will not only reducethe calcium carbonate of the limestone to lime or calcium oxid, but willalso produce a trisilicate of lime, which is the essential ingredient ofthe cement. In this manner a single burning only need be employed.

In practicing the invention the essential object to be secured is athorough commingling of the limestone, the slag, and the salt whichevolves oxygen at a high temperature to eliminate the sulfur. As a muchmore uniform mixture can be secured by applying the salt which is toevolve oxygen at the high temperate as a liquid solution, I prefer tofollow that method, and consequently the salt, preferably sodiumnitrate, or other salt of a similar nature will be dissolved and theother ingredients will be treated therewith. Preferably this solutionwill be added to the limestone, and the latter will then be ground, thegrinding beingawet process. The slag preferably will be in powderedform, such as now comes from blast-furnaces; but should it not bepowdered it will first be ground, and this grinding may take placesimultaneously with the grinding of the limestone. In any event afterthe limestone is ground in the wet state it will have added theretopowdered blast-furnace slag, and the whole will then be thoroughlyagitated to get an intimate mixture of the various ingredients. Theproportion of limestone t0 slag will depend upon the analysis of theslag; but care will be exercised to secure the proper proportion of limeto silica. A suitable proportion of ingredients will be from two andone-half to four pounds of nitrate of soda, one hundred pounds of slag,and from one hundred to one hundred and ten pounds of limestone,together with sufficient water to dissolve the nitrate of soda. Afterthese ingredients have been thoroughly mixed they will be burned in theusual way employed in the manufacture of ordinary cement, being eitherburned in powdered form or molded in bricks, as may be considered best,and being subjected to a very high heat for a number of hours. The heatmust be sufficiently high to cause a combination between the lime andslag to produce the trisilicate of lime, and this usually requires closeto 3,000 Fahrenheit. At a somewhat lower temperature the nitrate ofsodium will be broken down and the oxygen freed. This will convert thesulfid of calcium into a harmless sulfate of lime. The soda present willof course become part of the cement, and this is of considerableadvantage, because, as a rule, the slag is low in soda, and all cementshould contain not less than one per cent. of this element.

the nitrate of sodium. In the burning also the calcium carbonate orlimestone is converted into calcium oxid. I By following the processabove enumerated I am able to produce a cement of high grade, similar toPortland cement, and it is found to contain about twenty-three per cent.of silica, sixty-one per cent. of lime, nine per cent. of

This quantity is supplied by alumina, one and one-half per cent. ofsoda, small proportions of peroxid of iron, manganese, and magnesia, andonly nine-tenths per cent. of sulfur, which is present as a harmlesssulfate of lime. The cement produced in this Way will of course vary inproportion to the ingredients of the slag and the proportion of lime andnitrate of sodium added. The cement, however, will be fairly uniform, asthe slag from modern blast-furnaces varies but little in composition.The cementwill have all of the favorable qualities enumerated in mypatent above referred to, and as the original burning and handling ofthe limestone and lime are dispensed with it can be manufactured verycheaply, the'cost of grinding the limestone not quite compensating forthe cost of burning and handling the lime.

It will be understood, of course, that other soluble salts which evolveoxygen at a high temperature may be employed in place of the nitrate ofsodium, and all of the various salts enumerated in my previous patentare also adapted for carrying out the present process. The nitrate ofsodium is preferred by reason of its cheapness and also for the reasonthat it increases the proportion of soda in the coment.

. I am aware that it has been proposed to make cement by pulverizing andmixing together limestone or lime and blast-furnace slagand thereaftertreat the material with an aqueous solution of an alkali salt; but I amnot aware that it has ever been proposed to treat the limestone with asalt which will evolve oxygen at a high temperature and then grind thelimestone, after which it is mixed with powdered blast-furnace slag andburned.

What I claim as my invention, and desire to secure by Letters Patent, is

1. The herein-described process of forming cement which consists intreating limestone with a salt which will evolve oxygen at a hightemperature, grinding the same, thereafter mixing the same with powderedblast-furnace slag and then burning the mixture.

2. The herein-described process of forming cement which consists intreating limestone with a solution of a nitrate salt, grinding the same,thereafter mixing the ground mass with powdered blast-furnace slag, andthen burning the mixture.

3. The herein-described process of forming cement consisting in treatinglimestone with a solution of nitrate of sodium, grinding the same,thereafter mixing the ground mass with powdered blast-furnace slag, andthen burning the mixture.

In testimony whereof I, the said WILLIAM A. OTTO WUTH, have hereunto setmy hand. 60

WILLIAM A. OTTO WUTH. Witnesses:

ROBERT C. TOTTEN, F. W. WINTER.

